Superconducting single-photon detectors for GHz-rate free-space quantum communications
Alexander A. Verevkin, Jin Zhang, Wojciech Słysz, Roman Sobolewski, Andrey P. Lipatov, O. Okunev, Чулкова Галина Меркурьевна, Alexander A. Korneev, Gregory N Gol'tsman · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2002
We report our studies on the performance of new NbN ultrathin-film superconducting single-photon detectors (SSPDs). Our SSPDs exhibit experimentally measured quantum efficiencies from ~ 5% at wavelength λ = 1550 nm up to ~10% at λ = 405 nm, with exponential, activation-energy-type spectral sensitivity dependence in the 0.4-μm - 3-μm wavelength range. Using a variable optical delay setup, we have shown that our NbN SSPDs can resolve optical photons with a counting rate up to 10 GHz, presently limited by the read-out electronics. The measured device jitter was below 35 ps under optimum biasing conditions. The extremely high photon counting rate, together with relatively high (especially for λ > 1 μm) quantum efficiency, low jitter, and very low dark counts, make NbN SSPDs very promising for free-space communications and quantum cryptography.